Purpose: To examine the role of epidermal growth factor receptor (EGFR) signalling on ultrastructural organisation and remodelling of stromal corneal collagen fibrils (CF) and proteoglycans (PG) in the diabetic rat.
Methods: Diabetes was induced in female Wistar rats (n=5) by streptozotocin (STZ) injection (55mg/kg). Treatment with a selective inhibitor of EGFR tyrosine kinase, AG1478, was started on the same day as the induction of diabetes and administered every other day for four weeks. The corneas were fixed in 4% PFA at 4ºC to analyse the collagen fibril diameter. To study the distribution of proteoglycans the corneas were fixed in 2.5% glutaraldehyde in sodium acetate buffer containing cuprolinic blue. The analySIS soft imaging program was used to analyse CF and PG.
Results: In addition to a reduction in the epithelial thickness in the diabetic cornea, the median diameter and area fraction of CF in the stroma was decreased in diabetic rats compared to normal rats (p<0.001). In contrast, the median PG area and area fractions in diabetic rat corneas were significantly increased (p<0.001) compared to normal. Treatment with AG1478 prevented diameter and area fraction changes in CF and PG and restored corneas to a normal appearance.
Conclusions: These data show that the distribution of stromal CF and PG is altered in corneas after 4-weeks of diabetes. Furthermore, treatment with an inhibitor of EGFR signalling normalized these abnormalities. Thus our data suggest that the EGFR plays an important role in the development of diabetes-induced corneal remodelling.